U.S. President Barack Obama has extended the national emergency with respect to terrorist attacks on September 11, 2004, for another year, the White House said.

"Because the terrorist threat continues, the national emergency declared on September 14, 2001, and the powers and authorities adopted to deal with that emergency, must continue in effect beyond September 14, 2009," the presidential notice said.

"Therefore, I am continuing in effect for an additional year the national emergency the former President declared on September 14, 2001, with respect to the terrorist threat," the notice said.

The document has been sent to the Federal Register and transmitted to the Congress.

The September 11 attacks, often referred to as 9/11, were a series of coordinated suicide attacks by Al-Qaeda on the territory of the United States, which killed about 3,000 people.

In response to the attacks, the Bush administration declared a nationwide state of emergency, launched a "War on Terrorism", and enacted the USA PATRIOT Act.

The state of emergency, which gives the president additional powers in dealing with terrorism threat, has continued in full force and effect from 9/11 to the present.